Benabdallah El Hadj T, Astals S, Galí A, Mace S, Mata-Alvarez J
Department of Chemical Engineering, University of Barcelona, Martí i Franquès, no. 1, 6th floor, Barcelona 08028, Spain.
Water Sci Technol. 2009;59(6):1153-8. doi: 10.2166/wst.2009.100.
The anaerobic digestion of the organic fraction of municipal solid wastes is taking increasing importance in the recent years. The main problem of some anaerobic digestion process is the large quantity of ammonia that is released, especially when high solid digestion is implemented. A fraction of the supernatant is treated and the remaining is recirculated to maintain the reactor in the optimum solids concentration. The question arising is if this recirculation stream should also be treated to improve biogas production. However, when doing the latter the quantity of ammonia inside the reactor increases too which could lead to inhibit the reactor operation. In this paper it appears that not only free ammonia affects the methanogenic fermentation but also ammonium ion concentration. Biogas production profiles are estimated using the Gompertz model. On the other hand, inhibition constants are fitted using a non-competitive inhibition model equation Thus, 50% inhibition of biomethane production was observed at level of 215 and 468 mg NH3_N/L under mesophilic and thermophilic conditions. However, the methane generation under mesophilic and thermophilic conditions was reduced by 50% when ammonium ion reach concentrations of 3,860 and 5,600 mg NH4+_N/L respectively. Under mesophilic conditions, pH higher than 7 impacted the methanogens bacteria negatively. This threshold pH limit, is variable under thermophilic conditions, depending on the total ammonia concentration.
近年来，城市固体废物有机部分的厌氧消化变得越来越重要。一些厌氧消化过程的主要问题是释放出大量的氨，特别是在实施高固体消化时。一部分上清液经过处理，其余的则进行循环，以维持反应器处于最佳固体浓度。由此产生的问题是，这种循环流是否也应进行处理以提高沼气产量。然而，这样做时反应器内的氨量也会增加，这可能会导致抑制反应器运行。本文表明，不仅游离氨会影响产甲烷发酵，铵离子浓度也会产生影响。使用Gompertz模型估算沼气产量曲线。另一方面，使用非竞争性抑制模型方程拟合抑制常数。因此，在中温和高温条件下，当NH₃_N/L浓度分别达到215和468mg时，观察到生物甲烷产量受到50%的抑制。然而，当中温及高温条件下铵离子浓度分别达到3860和5600mg NH₄⁺_N/L时，甲烷生成量减少了50%。在中温条件下，pH高于7会对产甲烷菌产生负面影响。这个pH阈值在高温条件下是可变的，取决于总氨浓度。
